# How would a jetpack work?
**URL:** https://boards.straightdope.com/t/how-would-a-jetpack-work/947737
**Category:** Factual Questions
**Created:** [August 1, 2021, 1:02am UTC](https://boards.straightdope.com/t/how-would-a-jetpack-work/947737 "2021-08-01T01:02:47Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@Northern\_Piper](https://boards.straightdope.com/u/Northern_Piper)
#### Post date: [August 1, 2021, 1:02am UTC](https://boards.straightdope.com/t/how-would-a-jetpack-work/947737/1 "2021-08-01T01:02:47Z")
The LAX jetpack guy thread made me start to wonder: how would a jetpack work? What would the aerodynamics be? No wings; how would there be any stability?
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### Author:  [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)
#### Post date: [August 1, 2021, 2:25am UTC](https://boards.straightdope.com/t/how-would-a-jetpack-work/947737/2 "2021-08-01T02:25:02Z")
They aren’t jets like a jet plane (or _The Rocketeer_), they are jets like a SpaceX first stage, some lumbering thing that is just barely steerable.
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### Author:  [@Acierocolotl](https://boards.straightdope.com/u/Acierocolotl)
#### Post date: [August 1, 2021, 2:36am UTC](https://boards.straightdope.com/t/how-would-a-jetpack-work/947737/3 "2021-08-01T02:36:16Z")
Turbofan engines can generate adequate lift.
> **[Finally, the Jetpack We've Always Wanted](https://spectrum.ieee.org/finally-the-jetpack-weve-always-wanted)**
>
> Jetpack Aviation's JB-9 is a compact, high-performance jet turbine backpack that can fly for a solid 10 minutes
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### Author:  [@Acierocolotl](https://boards.straightdope.com/u/Acierocolotl)
#### Post date: [August 1, 2021, 2:44am UTC](https://boards.straightdope.com/t/how-would-a-jetpack-work/947737/4 "2021-08-01T02:44:38Z")
I wanted to add more and kinda submitted by accident.
This (and the rocket-powered one Darren G. is hinting at) worked by throwing a lot of thrust downwards to overcome gravity.
There’s a different variation where a person used a wingsuit, if memory serves, to generate lift, and a pair of turbofans to generate the thrust. He needed an airlaunch though, as he couldn’t generate enough lift for an unassisted takeoff.
> **[The electric wingsuits and jetpacks bringing bird-like abilities to humankind](https://eandt.theiet.org/content/articles/2021/07/avian-jealousy-complex-the-electric-wingsuits-and-jetpacks-bringing-bird-like-abilities/)**
>
> Electric wingsuits and kerosene jetsuits from BMW and Gravity Industries are fast-forwarding evolution, propelled by biomimicry, extreme sports and the meaning of life.
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### Author:  [@Bootb](https://boards.straightdope.com/u/Bootb)
#### Post date: [August 1, 2021, 2:45am UTC](https://boards.straightdope.com/t/how-would-a-jetpack-work/947737/5 "2021-08-01T02:45:32Z")
Some use water.
> **[JetLev](https://en.wikipedia.org/wiki/JetLev)**
>
> Pages for logged out editors learn more
>
>
> The JetLev is a water-propelled jet pack powered through a floater derived from jetski technology attached through an umbilical to the backpack which contains two nozzles and two control arms, in a configuration like traditional rocket belts and gas turbine jet belts. The JetLev also functions underwater, allowing users to dive into the water and jet back out. The jetpack can allow users to fly up to 10 m (30 feet) above the water. It was creat...
As far as I’m aware, none of them work particularly “well.” I don’t think that there have been many accidents, but that’s probably more a function of their rarity than anything else.
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### Author:  [@Acierocolotl](https://boards.straightdope.com/u/Acierocolotl)
#### Post date: [August 1, 2021, 2:58am UTC](https://boards.straightdope.com/t/how-would-a-jetpack-work/947737/6 "2021-08-01T02:58:41Z")
What you need is the military version.
> **[Watch these UK commandos fly over the sea with new jet pack | CNN Business](https://www.cnn.com/videos/business/2021/05/03/jet-suit-pack-british-royal-navy-zw-orig.cnn-business)**
>
> The British Royal Navy and Royal Marines tested out a jet suit developed by the company Gravity Industries. Gravity says its suit can fly up to 80 mph and climb to 12,000 feet in the air.
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### Author:  [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)
#### Post date: [August 1, 2021, 5:53am UTC](https://boards.straightdope.com/t/how-would-a-jetpack-work/947737/7 "2021-08-01T05:53:31Z")
The key to the success of that jet suit was the decision to put the jets on your arms.
And it’s not military per se, they are just trialling it.
[ ](https://www.youtube.com/watch?v=-a84uiajF1s)
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### Author:  [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)
#### Post date: [August 1, 2021, 6:00am UTC](https://boards.straightdope.com/t/how-would-a-jetpack-work/947737/8 "2021-08-01T06:00:25Z")
Here’s a clip on the development of it:
[ ](https://www.youtube.com/watch?v=EAJM5L9hhBs)
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### Author:  [@Senegoid](https://boards.straightdope.com/u/Senegoid)
#### Post date: [August 1, 2021, 6:05am UTC](https://boards.straightdope.com/t/how-would-a-jetpack-work/947737/9 "2021-08-01T06:05:11Z")
> [@Northern\_Piper](#):
>
> What would the aerodynamics be? No wings; how would there be any stability?
> [@Darren\_Garrison](#):
>
> . . . some lumbering thing that is just barely steerable.
This. Without airfoils or control surfaces like airplanes or helicopters, how is there any stability, and how are they steered? How does the pilot control where he goes? I haven’t seen any answers to this. IIRC, I asked the same in some earlier thread about jetpacks, and nobody gave any kind of meaningful answer that I recall.
> [@Richard\_Pearse](#):
>
> The key to the success of that jet suit was the decision to put the jets on your arms.
Is this it? Put the jets on the arms so you can flail them about to steer?
Do they have pitch, yaw, and roll jets like spacecraft that operate outside any atmosphere?
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### Author:  [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)
#### Post date: [August 1, 2021, 6:09am UTC](https://boards.straightdope.com/t/how-would-a-jetpack-work/947737/10 "2021-08-01T06:09:10Z")
Just point your arms in the appropriate direction. They seem to have quite precise control. The guy flying through the forest is obviously well practiced (he is the designer), but he has very good control of it.
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### Author:  [@Senegoid](https://boards.straightdope.com/u/Senegoid)
#### Post date: [August 1, 2021, 6:12am UTC](https://boards.straightdope.com/t/how-would-a-jetpack-work/947737/11 "2021-08-01T06:12:26Z")
> [@Richard\_Pearse](#):
>
> Just point your arms in the appropriate direction. They seem to have quite precise control. The guy flying through the forest is obviously well practiced (he is the designer), but he has very good control of it.
How does it maintain stability? What keeps the pilot from tumbling randomly? Airplanes have vertical and horizontal stabilizers for a reason – what equivalent is there in a guy flying a jetpack?
Is weight-and-balance and center of gravity as critical – or even more so – as in an airplane? How does he stay right-side-up?
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### Author:  [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)
#### Post date: [August 1, 2021, 6:54am UTC](https://boards.straightdope.com/t/how-would-a-jetpack-work/947737/12 "2021-08-01T06:54:28Z")
Did you watch the video about the development of it? There are the jets on his hands and one on his back, they form a tripod which makes it quite stable.
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### Author:  [@enipla](https://boards.straightdope.com/u/enipla)
#### Post date: [August 1, 2021, 10:53am UTC](https://boards.straightdope.com/t/how-would-a-jetpack-work/947737/13 "2021-08-01T10:53:53Z")
I would think your arms would get quite tired just trying to point the things in the right direction.
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### Author:  [@scudsucker](https://boards.straightdope.com/u/scudsucker)
#### Post date: [August 1, 2021, 11:33am UTC](https://boards.straightdope.com/t/how-would-a-jetpack-work/947737/14 "2021-08-01T11:33:41Z")
I imagine the Royal Marines depicted have somewhat more upper body strength than you or I, and they do not appear to be struggling with control.
I would question what happens when one unit fails (no doubt the reason for dual ducted fans - if they are actually ducted fans) for each hand, but loss of any of the three “legs” of a tripod would be catastrophic. I assume they have some way to trigger a parachute that can be done while spinning chaotically.
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### Author:  [@GreenWyvern](https://boards.straightdope.com/u/GreenWyvern)
#### Post date: [August 1, 2021, 12:44pm UTC](https://boards.straightdope.com/t/how-would-a-jetpack-work/947737/15 "2021-08-01T12:44:03Z")
Alternatively, if you’re good at balancing…
[ ](https://www.youtube.com/watch?v=VAit7ZtetrA)
It has a computerised logic system built in to help with balancing, but it still requires 50-100 hours training to use.
However, Franky Zapata did fly across the English Channel on it at speeds of up 160 km/h (100 mph), and it can go high enough to need an oxygen mask.
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### Author:  [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)
#### Post date: [August 1, 2021, 1:31pm UTC](https://boards.straightdope.com/t/how-would-a-jetpack-work/947737/16 "2021-08-01T13:31:55Z")
> [@Senegoid](#):
>
> [helicopters:] how is there any stability…?
Helicopters are inherently unstable. 😉
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### Author:  [@mbh](https://boards.straightdope.com/u/mbh)
#### Post date: [August 1, 2021, 2:55pm UTC](https://boards.straightdope.com/t/how-would-a-jetpack-work/947737/17 "2021-08-01T14:55:59Z")
[Photo of an old-style rocket belt.](https://en.wikipedia.org/wiki/Jet_pack#/media/File:Rocket_man02_-_melbourne_show_2005.jpg)
In this photo, you can see the traditional design of older models of jetpacks. A heavy fuel tank is on one side. Your body is on the other side. The jet thrusts upward through the vertical centerline of the mass. The jet is above the horizontal centerline of the mass. Your weight keeps the jet pointing downward, and the thrust pointing upward. You steer by shifting your weight, making the jet lean slightly sideways. When you stop actively interfering, your weight will return the jet to a vertical orientation.
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### Author:  [@gnoitall](https://boards.straightdope.com/u/gnoitall)
#### Post date: [August 1, 2021, 3:04pm UTC](https://boards.straightdope.com/t/how-would-a-jetpack-work/947737/18 "2021-08-01T15:04:02Z")
> [@Johnny\_L.A](#):
>
> Helicopters are inherently unstable
Negative flight stability is a defining characteristic of modern high-performance warplanes, going back to the F-16.
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### Author:  [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)
#### Post date: [August 1, 2021, 3:06pm UTC](https://boards.straightdope.com/t/how-would-a-jetpack-work/947737/19 "2021-08-01T15:06:01Z")
That’s true. But in general, if you let go of the stick/yoke in an airplane, it will return to equilibrium. If you let go of the cyclic in a helicopter, you’ll quickly be out of control.
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### Author:  [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)
#### Post date: [August 2, 2021, 2:27am UTC](https://boards.straightdope.com/t/how-would-a-jetpack-work/947737/20 "2021-08-02T02:27:34Z")
Yep agreed. It is obviously designed for someone with reasonable physical strength. Average lardarses like me would tire very quickly I think.
> [@scudsucker](#):
>
> I would question what happens when one unit fails (no doubt the reason for dual ducted fans - if they are actually ducted fans) for each hand, but loss of any of the three “legs” of a tripod would be catastrophic. I assume they have some way to trigger a parachute that can be done while spinning chaotically.
That is the reason they stay low. At the time the Wired video was made, there was no control or safety device to save a failed engine. It is supposed to be able to fly up 2000’ but nobody wants to fall that far!
This video follows an average Joe who buys a jet suit.
> **[I got to test drive a $440,000 flying jet suit — it was terrifying and...](https://www.cnbc.com/2018/10/22/i-got-to-test-drive-a-440000-flying-gravity-jet-suit.html)**
>
> Richard Browning, CEO of Gravity Industries and the inventor of the Gravity Jet Suit, invited CNBC senior executive producer Ray Parisi to try out his insane invention.
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